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Date: Mon, 4 Aug 2008 13:43:28 -0700
Subject: socket_select() problem
From: ian@digg.com (Ian Eure)

Hi, I have a problem with socket_select(). I hope someone here can  
point me in the right direction, because I'm stumped.

Basically, I'm getting this error:

Warning: socket_select() [function.socket-select]: no resource arrays  
were passed to select in Net/Gearman/Client.php on line 197

This is using the Net_Gearman PEAR package to submit a Gearman job.  
The job is submitted and runs to completion; this message is displayed  
by the caller.

The relevant code is here:
http://code.google.com/p/netgearman/source/browse/trunk/Net/Gearman/Client.php#197

             $write  = null;
             $except = null;
             $read   = $this->conn;
             socket_select($read, $write, $except, 10);

If I add var_dump($read) on the line above socket_select(), I get:
array(2) {
   [0]=>
   resource(141) of type (Socket)
   [1]=>
   resource(142) of type (Socket)
}

The error message appears to be spurious. This is where the socket is  
created:

             $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
             @socket_connect($socket, $host, $port);
             $errorCode = socket_last_error($socket);

             socket_set_nonblock($socket);
             socket_set_option($socket, SOL_TCP, 1, 1);

I removed the @, and there were no errors being hidden. I resorted to  
examining the socket extension code, and these are my findings:

socket_select() calls php_sock_array_to_fd_set() on $read / $write /  
$except:
http://cvs.php.net/viewvc.cgi/php-src/ext/sockets/sockets.c?revision=1.199&view=markup#l788

If the result of all three of those operations is zero, the error  
message is displayed.

php_sock_array_to_fd_set() checks to see if the argument it got is an  
array:
http://cvs.php.net/viewvc.cgi/php-src/ext/sockets/sockets.c?revision=1.199&view=markup#l710
If not, it returns zero.

php_sock_array_to_fd_set() calls zend_fetch_resource():
http://cvs.php.net/viewvc.cgi/php-src/ext/sockets/sockets.c?revision=1.199&view=markup#l716

If that returns zero for every element in the array,  
php_sock_array_to_fd_set() also returns zero.

Since I'm dumping $read directly before the socket_select() call, it  
seems that the zend_fetch_resource() call is what's failing.

I wrote a simple testcase that submits a single job to Gearman. If I  
run it under Apache2, I get the socket_select() warning. If I run it  
from the CLI, I don't. I'm also pointing the CLI at the Apache2  
php.ini file. At this point, I don't know how to track this any  
further. If I was getting the same error on the CLI, I could trace it  
with gdb. I don't know how I'd go about doing something like that for  
an Apache extension.

I'm running PHP 5.2.0 under Debian Etch, installed from the vanilla  
Debian packages (5.2.0-8+etch1). I have APC and Memcache extensions  
installed from PECL. I disabled both, and there was no change in what  
I'm seeing. I also emailed everyone listed in socket.c, but I got no  
response.

I'm at a loss. Where do I go from here?

  - Ian